apollo-upload-client 12.0.0 on Node.js NPM

Major

Updated Node.js support from v8.5+ to v8.10+, to match what the eslint dev dependency now supports. This is unlikely to be a breaking change for the published package.

Updated dev dependencies.
Added the eslint-plugin-jsdoc dev dependency.
Replaced the size-limit dev dependency with @size-limit/preset-small-lib.
Only create a default AbortController instance if signal is not already set in fetch options, fixing #162 via #169.
Use GitHub Actions instead of Travis for CI.
Clarified that Opera Mini isn’t supported in the Browserslist queries and readme “Support” section.
Documented polyfills to consider in the readme “Support” section.
Updated examples to use @apollo/react-hooks.